Display omitted
•Synthesis of polyesters by ring-opening polymerization is reviewed.•Method of moments are detailed for different cases.•Step-by-step guide on how to combine the method of moments in ...modeling is formulated.
Polyesters produced from cyclic monomers, including polylactic acid (PLA), polycaprolactone (PCL) and polybutylene terephthalate (PBT), are widely used in different applications, ranging from household items to medical implants. These polymers can be produced by various processes, but ring-opening polymerization (ROP) occupies an important position. In this sense, ROP represents the foremost route used by both academia and industry to synthesize these polymers. In this review, we discuss the synthesis of PLA, PCL, PBT and some of their copolymers by ROP, focusing on polymerization kinetics and molecular weight control. We also revisit the most representative deterministic mathematical models for ROP to produce these polymers. We formulate a step-by-step guide on how to combine the method of moments in modeling the synthesis of polymers by ROP, including details on how to handle multiple summations in the system of Ordinary Differential Equations generated from the modeling.
Background: Preterm rupture of membranes (PROM) affects 3% of pregnancies, with 0.4% experiencing second-trimester ROM. Gestational age at PROM strongly influences outcomes. Neonatal survival rates ...vary by gestational age. Short latency (<48 hours) after viability (>24 weeks) is associated with adverse outcomes. Objectives: Analyze maternal and neonatal outcomes in patients with previable rupture of membranes (PPROM) between 20-28 weeks of pregnancy. Patients and methods: Retrospective study at Qena University Hospital (June 2020-June 2022) on singleton pregnancies with PPROM. Inclusion criteria: no active labor, chorioamnionitis, fetal anomalies, iatrogenic ROM, or multiple gestations. Data collected: maternal demographics, obstetric history, gestational age at ROM, delivery, interventions; neonatal data including birth weight, Apgar scores, NICU admission, diagnoses, survival. Results: The mean age 26.72 ± 5.51 years and BMI 25.18 ± 4.44 kg/m^2, with 9.38% underweight, 37.5% normal weight, 34.38% overweight, and 18.75% obese. The average gravidity was 3 with a range of 0-8. Parity averaged 2 with a range of 0-7. The mean number of abortions was 1 with a range of 0-5, with 26.56% history of preterm labor. Maternal complications included chorioamnionitis (12.5%), sepsis (4.69%), and cord prolapse (7.81%). Neonatal viability was 67.19%. Among viable fetuses (N = 43), Apgar scores (1 min: 6.7 ± 2.32, 5 min: 7.07 ± 2.45), NICU admission (62.79%, stay: 8.01 ± 5.94 days), and NICU survival (37.21%, N = 35), with 74.42% overall viability. Conclusion: Challenges in early preterm births highlight the need for tailored care. Adverse neonatal outcomes underscore the necessity of targeted strategies for this vulnerable population.
Poly(β‐hydroxyalkanoate)s (PHAs) are a class of aliphatic polyesters that can be efficiently synthesized by ring‐opening polymerization (ROP) of β‐lactones. The case of chiral racemic β‐substituted ...β‐lactones is particularly appealing since these monomers open the way to original tacticities and materials different from those biotechnologically produced. In this overview, after briefly surveying general considerations associated to the ROP of β‐lactones and metal‐based catalysts used in stereoselective ROP of racemic β‐butyrolactone, special emphasis is given to discrete rare earth catalysts that have allowed the preparation of highly syndiotactic poly(3‐hydroxybutyrate)s. Recent developments – such as preparation of stereocontrolled PHAs with pendant structural groups via (co)polymerization of functional β‐substituted β‐lactones, and highly alternating copolymers obtained by ROP of mixtures of enantiomerically pure but different monomers – are also discussed.
Rare earth catalysts have recently allowed the efficient preparation of highly syndiotactic PHBs from racemic β‐butyrolactone. These catalysts also provide access to original materials such as PHAs with pendant structural groups via (co)polymerization of functional β‐substituted β‐lactones or highly alternating copolymers prepared by ROP of mixtures of enantiomerically pure but different monomers. The outlook for this research area is discussed.
The roles of Rho family guanosine triphosphatases (GTPases) of plants (ROPs) in modulating plant growth and development have been well characterized. However, little is known about the roles of ROP ...signaling pathways in regulating plant autophagy and autophagosome formation. In this study, we identify a unique ROP signaling mechanism, which mediates developmental to autophagic transition under stress conditions in the model plant Arabidopsis. Loss-of-function mutants of ROP8 showed stress-induced hypersensitive phenotypes and compromised autophagic flux. Similar to other ROPs in the ROP/RAC family, ROP8 exhibits both plasma membrane and cytosolic punctate localization patterns. Upon autophagic induction, active ROP8 puncta colocalize with autophagosomal markers and are degraded inside the vacuole. In human cells, RalB, an RAS subfamily GTPase, engages its effector Exo84 for autophagosome assembly. However, a RalB counterpart is missing in the plant lineage. Intriguingly, we discovered that plant ROP8 promotes autophagy via its downstream effector Sec5. Live-cell super-resolution imaging showed that ROP8 and Sec5 reside on phagophores for autophagosome formation. Taken together, our findings highlight a previously unappreciated role of an ROP8-Sec5 signaling axis in autophagy promotion, providing new insights into how plants utilize versatile ROP signaling networks to coordinate developmental and autophagic responses depending on environmental changes.
Rho of plants (ROP) signaling plays important roles in regulating plant growth and development. This study identified and characterized a plant-unique ROP8-Sec5 signaling axis that promotes autophagy and autophagosome formation under stress conditions.
Retinopathy of prematurity (ROP) is a serious morbidity in neonates, which could lead to poor visual outcomes. Data from high-income countries suggest a high incidence of this disease among very ...preterm neonates.
The objective of this study was to evaluate incidence and risk factors of ROP in very-low-birth-weight (VLBW) neonates.
VLBW neonates born between January 2015 and July 2018 at Sir Ganga Ram Hospital, New Delhi, were prospectively screened for ROP. The risk factors for ROP were analyzed.
Of 461 VLBW infants born during the study period, 361 survived beyond 4 weeks and were evaluated for ROP. Of these, 43 (11.9%) neonates had ROP (any stage) and 8 (2.2%) required treatment with either laser ablation or intraocular anti-vascular endothelial growth factor (anti-VEGF) injections. On multiple logistic regression analysis, lower gestational age, apnea of prematurity, and red cell transfusion were independent risk factors for retinopathy of prematurity.
We observed a low incidence of ROP requiring treatment in VLBW neonates. Lower gestation, apnea of prematurity, and red cell transfusions were independent risk factors for ROP.
The enzymatic ring-opening copolymerization (eROP) of globalide (Gl) and pentadecalactone (PDL) was performed in solution from mixtures of the two macrolactones at ratios covering the whole range of ...comonomeric compositions. The resulting P(Gl
-
-PDL
) random copolyesters were aminofunctionalized by thiol-ene reaction with aminoethanethiol. ROP of γ-benzyl-l-glutamate
-carboxyanhydride initiated by P(Gl
-
-PDL
)-NH
provided neutral poly(γ-benzyl-l-glutamate)-grafted copolyesters, which were converted by hydrolysis into negatively charged hybrid copolymers. Both water-soluble and nonsoluble copolymers were produced depending on copolymer charge and their grafting degree, and their capacity for self-assembling in nano-objects were comparatively examined. The emulsion solvent-evaporation technique applied to the chloroform-soluble copolymers grafted with benzyl glutamate rendered well-delineated spherical nanoparticles with an average diameter of 200-300 nm. Conversely, micellar solutions in water were produced from copolyesters bearing grafted chains composed of at least 10 units of glutamic acid in the free form. The copolymer micelles were shown to be able to load doxorubicin (DOX) efficiently through electrostatic interactions and also to release the drug at a rate that was markedly pH dependent.
Purpose:
To study the features of “nontype 1” retinopathy of prematurity (ROP) and indications of treatment.
Design:
Retrospective study.
Methods:
Medical records of inborn or outborn neonates ...screened for ROP from tertiary level special newborn care unit according to national screening guidelines were analyzed. Infants diagnosed with milder than type 1 ROP, not progressing to type 1 ROP, with complete medical records were included. Features, morphology, staging and indications of treatment were recorded. Preplus disease was studied as a risk factor for treatment.
Results:
464 eyes (232 infants) were screened. Thirty eyes of 16 infants with non-type 1 ROP were included. Twelve out of 30 such eyes (40.0%) underwent treatment. Three had type 2 ROP, all of which were treated, 27 had mild type ROP, 9 of which were treated. So, out of 12 eyes, 3 (25.0%) were treated due to structural abnormalities (anteroposterior traction on retina, flat retinal fibrosis, vitreous hemorrhage) and 9 out of 12 eyes (75.0%) due to persistent ROP. Eyes with preplus disease were 2.33 times more likely to be treated; presence of preplus disease came out to be a significant risk factor for treatment.
Conclusions:
Persistent ROP with increasing weight and structural abnormalities were the major indication of treatment in milder than type 1 ROP. Presence of preplus disease was also an important risk factor for treatment.
During growth and morphogenesis, plant cells respond to mechanical stresses resulting from spatiotemporal changes in the cell wall that bear high internal turgor pressure. Microtubule (MT) arrays are ...reorganized to align in the direction of maximal tensile stress, presumably reinforcing the local cell wall by guiding the synthesis of cellulose. However, how mechanical forces regulate MT reorganization remains largely unknown. Here, we demonstrate that mechanical signaling that is based on the Catharanthus roseus RLK1-like kinase (CrRLK1L) subfamily receptor kinase FERONIA (FER) regulates the reorganization of cortical MT in cotyledon epidermal pavement cells (PCs) in Arabidopsis. Recessive mutations in FER compromised MT responses to mechanical perturbations, such as single-cell ablation, compression, and isoxaben treatment, in these PCs. These perturbations promoted the activation of ROP6 guanosine triphosphatase (GTPase) that acts directly downstream of FER. Furthermore, defects in the ROP6 signaling pathway negated the reorganization of cortical MTs induced by these stresses. Finally, reduction in highly demethylesterified pectin, which binds the extracellular malectin domains of FER and is required for FER-mediated ROP6 activation, also impacted mechanical induction of cortical MT reorganization. Taken together, our results suggest that the FER-pectin complex senses and/or transduces mechanical forces to regulate MT organization through activating the ROP6 signaling pathway in Arabidopsis.
•Mechanical stresses rapidly promote ROP6 activation and microtubule rearrangement•FER and ROP6 affect mechanical-stress-induced microtubule rearrangement•FER and RopGEF14 are required for the ROP6 activation induced by mechanical stress•Pectin demethylesterification affects ROP6 activation induced by mechanical stress
Tang et al. show that FER participates in sensing and/or transducing mechanical signal to directly regulate MT reorganization in the control of cell expansion and cell shape formation. This study elucidates a mechano-transducing pathway (the pectin-FER-ROP-MT pathway) connecting mechanical stress to cell morphogenesis in plants.
Background
Stage 5 retinopathy of prematurity is a difficult condition to treat despite technological advances in vitreous surgery.
Methods
A retrospective chart review of all consecutive cases of ...stage 5 ROP was performed between December 2016 and December 2018, and 21 babies were included for assessment of surgical outcomes using a modified vitrectomy technique. Data extracted from documents included demography, ROP screening status, preoperative prophylactic therapy, clinical presentation, surgery performed, and postsurgical outcomes.
Results
Out of the 21 babies, ophthalmologist screening was done in 42.9%. Mean birth weight was 1185 ± 222.4 g with a mean gestational age of 29.86 ± 2.0 weeks and mean post-menstrual age of 44.55 ± 9.82 weeks. Lesser than stage 5 disease was seen in 16.7% of eyes and they were managed accordingly. Seventy percent of babies had bilateral disease. 21 eyes underwent 25-gauge pars plicata vitrectomy using a modified technique. After an average follow-up duration of 6.33 ± 2.18 months, the final macular attachment rate was 19%. Anteriorly closed-posteriorly closed type configuration of retinal detachments had a poorer outcome. Fix and follow visual acuity was achieved in 23.8% of eyes, while 57.1% of eyes had a perception of light.
Conclusions
Management of stage 5 ROP is mostly surgical; however, the risk of ending up with a poor vision or vision loss is high, irrespective of whether surgery is performed. The modified surgical technique with a spacer described in this study may help in better manipulation of instruments inside the vitreous cavity.
Choroidal thickness and ocular growth in childhood Prousali, Efthymia; Dastiridou, Anna; Ziakas, Nikolaos ...
Survey of ophthalmology,
March-April 2021, 2021 Mar-Apr, 2021-03-00, 20210301, Letnik:
66, Številka:
2
Journal Article
Recenzirano
The involvement of the choroid in ocular growth regulation has been postulated in studies showing that refractive errors correlate with alterations in choroidal thickness (ChT). The advent of optical ...coherence tomography imaging has enabled qualitative and quantitative assessment of the choroid. In children, ChT changes correlate with a number of ocular pathologies, including myopia, retinopathy of prematurity, and amblyopia. We synthesize mechanisms and evidence regarding choroidal thickness variation during childhood. Subfoveal ChT is influenced by a number of factors including age, ethnicity, gender, axial length, and intraocular pressure. Myopic eyes have thinner choroids compared to emmetropic and hyperopic eyes. ChT may in fact serve as a marker of myopic progression, as ChT thinning occurs early during myopic development, but this association has not been established quantitatively. In addition, subfoveal ChT appears thicker in amblyopic eyes, while prematurity and retinopathy of prematurity may be associated with thinner ChT. Overall, both animal models and clinical research indicate that ChT induces or reflects physiological changes in the eye pertaining to ocular growth or maturation.
PDF
